On an annualized basis, Japan's economy grew 1 percent in the fourth quarter against expectations for a 2.8 percent rise.

"We thought there might be a chance of a weaker number, because despite a pick-up in consumption we have had weaker export data and disappointing machinery orders data for December," Alvin Liew, senior economist at UOB told CNBC Asia Squawk Box.

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Pedestrians cross a road while carrying umbrellas as snow falls in Tokyo, Japan.

"The weak data does reinforce our expectations that the Bank of Japan will come in with additional monetary stimulus and we are looking at an additional 10 trillion yen perhaps this year," he added.

The BOJ concludes a two-day policy meeting on Tuesday and is not expected to make any changes to its monetary policy given that it already has a hefty asset-purchase program in place.

Analysts have been anticipating an expansion of that stimulus to offset the impact of a planned rise in Japan's sales tax in April.

Japanese markets appeared to shrug off the weaker-than-expected economic data in their stride, with the benchmark Nikkei-225 stock index opening 0.2 percent higher.

Still, the slowing momentum in Japan's economy was a worrying sign especially as the country braces for the impact of the sales-tax hike, analysts said.

"The momentum has gone in Japan," said Paul Donovan, deputy head of global economics at UBS. "What would help Abe is the TPP [Trans-Pacific Partnership].That [trade deal] would give [Prime Minister Shinzo] Abe an external force to go to the internal grups that areresisting change."